Fine Structure of Retinae of Cephalopods (Todarodes pacificus And Octopus minor) Inhabiting the Korean Waters I

한국 연근해산 두족류 (Todarodes pacificus And Octopus minor) 망막 (Retina)의 미세구조 I

  • Han, Jong-Min (Department of Life Science, College of Natural Science, Mokwon University) ;
  • Chang, Nam-Sub (Department of Life Science, College of Natural Science, Mokwon University)
  • 한종민 (목원대학교 자연과학대학 생명과학부) ;
  • 장남섭 (목원대학교 자연과학대학 생명과학부)
  • Published : 2002.03.01

Abstract

The retinae of Todarodes pacificus and Octopus minor are divided into four layers that are an outer segment, a rod base region, an inner segment, and a plexiform layer, respectively. The retina of Octopus minor is about $20{\mu}m$ thicker ($400{\sim}420{\mu}m$) than that of Todarodes pacificus ($385{\sim}400{\mu}m$). A retina is composed of visual cells and supporting cells. The microvilli of length $0.6{\sim}0.7{\mu}m$ are packed densely on top of the supporting cells of Octopus minor while they are not found in Todarodes pacificus. The visual cells and supporting cells have pigment granules that exclude light. In case of Todarodes pacificus, the pigment granules of the visual cell are larger ($2.0{\times}0.5{\mu}m$) than those of the supporting cell ($1.0{\times}0.3{\mu}m$). But, the sizes of both cells are similar in Octopus minor. In the upper portion of a visual cell, microvilli shaped like a comb are forming a rhabdome (diameter, 60 nm) of a hexagonal structure. The rhabdome consists of 4 rhabdomere and the total area of a rhabdom of Octopus minor is larger than that of Todarodes pacificus. The synaptosome constructing a plexiform layer in Todarodes pacificus are divided into two types, each of which possess electron dense-core vesicles and electron lucent vesicles, respectively. Octopus minor also has two types of synaptosomes but each type comprises a mixture of electron dense vesicles and electron lucent vesicles, and electron lucent vesicles only, respectively, which is different from the case of Todarodes pacificus.

살오징어 (Todarodes pacif icus)와 서해낙지 (Octopus minor)의 망막은 외절부, 간상기저부, 내절부 그리고 망상층 등 4개의 층으로 구분되었고, 망막의 두께는 오징어 ($385{\sim}400{\mu}m$)에서보다 낙지 ($400{\sim}420{\mu}m$)에서 $20{\mu}m$ 정도 더 두터웠다. 망막은 시각세포와 지지세포로 구성되어 있는데, 서해낙지의 지지세포 상단에는 미세융모 (길이 $0.6{\sim}0.7{\mu}m$)가 밀생된데 비해 살오징어에서는 확인되지 않았다. 망막을 구성하는 시각세포와 지지세포들은 광선을 차단하는 색소과립들을 소지하고 있었는데, 살오징어인 경우 시각세포의 색소과립(크기, $2.0{\times}0.5{\mu}m$ 정도)이 지지세포의 색소과립 (크기, $1.0{\times}0.3{\mu}m$ 정도)에 비해 컸으나, 서해낙지에서는 두 세포간 색소과립의 크기 ($0.8{\times}0.6{\mu}m$ 정도)가 비슷하였다. 시각세포의 세포질 상단부에서 빗살모양의 미세융모들이 정육각형 구조 (직경, 60 nm)인 rhabdome을 형성하였는데 한 개의 rhabdome은 4개의 rhabdomere로 구성되어 있으며, 전체 rhabdome의 총 단면적은 서해낙지가 살오징어에 비해 두 배정도 컸다. 망상층을 구성하는 연접체는 살오징어인 경우 전자밀도가 높은 핵을 포함하는 소포 (electron dense-core vesicle)와 전자밀도가 낮은 소포 (electron lucent vesicle)들로만 형성된 연접체 등 두 종류를 소지한 반면, 서해낙지에서는 전자밀도가 높은 소포(electron dense vesicle)와 전자밀도가 낮은 소포들이 혼합된 형과 전자밀도가 낮은 소포들로만 이루어진 연접체 등 두 종류를 소지하고 있어 두 종간 차이가 확인되었다.

Keywords

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